PHOENIX — A federal judge ruled Wednesday that Arizona authorities can enforce the most contentious section of the state’s immigration law, which critics have dubbed the “show me your papers” provision.

The ruling by U.S. District Judge Susan Bolton clears the way for police to carry out the 2010 law’s requirement that officers, while enforcing other laws, question the immigration status of those who they suspect are in the country illegally.

The requirement has been at the center of a two-year legal battle that culminated in a U.S. Supreme Court decision in June upholding the requirement.

Opponents then asked Judge Bolton to block the requirement, arguing that it would lead to systematic racial profiling and unreasonably long detentions of Hispanics if it’s enforced.

Attorneys for Arizona Gov. Jan Brewer urged the judge to let the requirement go into effect, saying the law’s opponents were merely speculating in their racial profiling claims, that police have received training to avoid discriminatory practices and that officers must have “reasonable suspicion” that a person is in the country illegally to trigger the requirement.

In her ruling, Judge Bolton said the court will not ignore the clear direction from the Supreme Court that the provision “cannot be challenged further on its face before the law takes effect.”

She reiterated the high court’s interpretation that the law might be able to be challenged as unconstitutional on other grounds.

Among the opponents of the law was the Obama administration, which challenged the law based on the argument that federal immigration law trumped Arizona law. The challenge didn’t confront racial profiling. The administration failed to persuade the nation's highest court to strike down the questioning requirement.

To the supporters of Arizona’s law, the questioning requirement was the most important part of the statute, whose stated purpose was to reduce the problems associated with illegal immigration through enforcement the state’s policy.

Less-controversial sections of the law have been in effect since late July 2010, but rarely have been used.

Arizona’s law was passed amid voter frustration with the state’s role as the busiest illegal entry point into the country. Five states — Alabama, Georgia, Indiana, South Carolina and Utah — have adopted variations on Arizona’s law.

Mrs. Brewer’s office said the law is expected to go into effect shortly.

“The courts have now consistently found that the plaintiffs have not met the high bar in arguing this law needs to be enjoined before it’s allowed to take effect,” gubernatorial spokesman Matthew Benson said. “Certainly, Gov. Brewer is pleased with this decision. She believes it’s time S.B. 1070 is implemented and so that we can see how effective this law is in practice.”

Karen Tumlin, an attorney for the National Immigration Law Center, said her office was “considering our legal options” after Judge Bolton’s ruling.

“We were surprised and disappointed,” said Dan Pochoda, legal director for the American Civil Liberties Union of Arizona.

Judge Bolton did, however, grant a preliminary injunction against a statute making it illegal to harbor people suspected of being in the country illegally.